This invention relates to circuit breakers with ground fault interruption capability with a visual indicator of a ground fault trip that differentiates from an overload trip.
Ground fault circuit breakers are known in which the elements of a circuit breaker as normally devised for overload current protection are combined with the elements of a ground fault circuit interrupter and packaged together for a location at a load center. A representative example is that of Coley et al. U.S. Pat. No. 4,081,852, Mar. 28, 1978, which is incorporated by reference herein and describes an arrangement including a ground fault detector in side-by-side relation with a circuit breaker with interconnection therebetween so that breaker contacts are tripped open upon the occurrence of either a current overload condition or a ground fault condition.
Ground fault circuit breakers normally have an external handle for manual switching and trip indication. The handle has ON, OFF, and TRIP positions so that upon examination a user can tell if the breaker has tripped. Such apparatus has been widely and successfully used. It is the case, however, that a trip of the breaker is indicated in the same manner by the handle regardless of the cause of the trip, whether it be an overload condition or a ground fault condition.
There is interest in providing a ground fault circuit breaker with an indicator that shows the user if a trip is due to a ground fault condition, rather than an overload, so that any system condition causing a trip can be more readily identified and corrected. A ground fault circuit breaker with a ground fault trip indicator, that is not responsive to overload trips, is disclosed in copending application Ser. No. 175,976, filed Aug. 7, 1980, by R. Davidson and J. Misencik which is herein incorporated by reference and describes an arrangement in which an additional circuit branch in the ground fault interrupter portion of the ground fault circuit breaker is energized to turn on an indicating light or the like upon the occurrence only of a ground fault trip. The arrangement of the copending application is effective but because of the electrical components required entails additional cost that is desired to be avoided.
In accordance with the present invention, a ground fault trip in a ground fault circuit breaker is indicated by a mechanical arrangement operable without additional electrical components to those existing in the ground fault circuit breaker. The arrangement utilizes the motion of the trip solenoid that occurs upon a ground fault trip to open the breaker contacts. The general idea is for the solenoid's plunger movement to release a spring loaded mechanical element that then extends from the breaker unit indicating a ground fault trip. More specifically, the mechanical element may be a button that is in a normally depressed location from the exterior of the unit. Attached to the button is a spring biasing it outwardly and a latch which holds the button in the depressed location in the absence of a trip. A latch arm is located so that it is subject to unlatching when a means for actuating opening of the breaker contacts is moved by the inward motion of the solenoid plunger. After the breaker is reset to ON, the ground fault indicating button can be depressed and relatched.
In this way, the desired ground fault indicating function, with the ability to differentiate a ground fault trip from other trips, is achieved merely by the addition of the indicating button and its spring and latch assembly. The electrical arrangement of the circuit breaker remains unchanged and the mechanical elements required are economical to implement .